The world’s largest California redwood grove – in Birr?

Giants are nothing new at Birr Castle Estate. In the early 1830s the third earl of Rosse designed and built a reflecting telescope that for almost a century was the largest in the world. A more recent addition to the demesne, the children's play area, has the biggest turreted treehouse in Ireland. And in the storms of February 2014 a grey poplar that, at 42m, was generally recognised as the tallest tree in the British Isles came crashing to the ground.

But now Birr, in Co Offaly, is going even bigger. Twenty acres of the castle gardens has been set aside to plant a grove of giant sequoias and coast redwoods. The largest living trees on the planet, they can reach heights of 100m or more – usually in northern California – and if the grove reaches its target total of 3,000 it will be the largest assemblage of these trees in the world.

Anyone who has €500 or more to spare can go to the website www.giantsgrove.ie and sponsor an individual tree, or a group of trees, as a tribute to family who are living, or have lived, abroad.

It's the project of the present Lord Rosse, Brendan Parsons, who turned 80 on October 21st, and Crann: Trees for Ireland, which celebrates its 30th anniversary this year.

Isn’t it a bit of a mad idea?

“I think it’s a marvellous idea,” Parsons says. “We are experimenters by nature. Trying new things at Birr is an old tradition. It’s absolutely cut out for Birr, this. We never do what other people do. The redwood grove will add a fantastic new dimension to Birr Castle Demesne, in line with the projects we already have going here – and also because of the new concept of a different sort of diaspora, an arboreal diaspora.”

We’re sitting in the room that the family calls the botanical library, its shelves crammed with plant and tree books, ancient and modern. It’s a cosy room, especially with a fire burning in the stove.

But Offaly is a long way from northern California. Will the climate of the Irish midlands – especially Birr, famous for low winter temperatures and all those “brr” jokes – be congenial to this botanical bigfoot?

“At the moment we have nine redwoods growing in ones and twos across the demesne: four of one species, five of the other,” Parsons says. “They were probably planted around the time of the third earl’s death, in the 1860s. I’ve often puzzled over why each one was planted where it was. I don’t think there was a concept of landscaping in those days. It was more a case of put one here, one there, and see how they’d go. But the ones that seem to thrive here are the coast redwoods. The tree that has done best in girth is in the wettest possible place.”

Let loose

When we don our coats and head across the gardens it becomes clear that although Parsons may have reached an august age, and be the keeper of a solemn aristocratic legacy stretching back to 1620, when it comes to trees he is more like a child who has been let loose on a bouncy castle. As we walk he points out various specimens, describing them with obvious delight, including that fallen poplar, now lying in horizontal splendour on the banks of the River Camcor.

“There’s a long tradition at Birr of planting trees to mark birthdays and other anniversaries,” he says. “The tree that marked my entry into the world is a magnolia – now, therefore, 80, and a champion in its own field – and we’ve planted trees for the children and grandchildren. For our silver wedding we planted a grove of native silver birch.”

Won’t people quibble with the choice of redwoods, rather than a native tree, for this “diaspora” project? “It’s a returned native,” he says. “It grew here about two or three ice ages ago, so why not try again?”

He cites the successful return of our native pine, now called the Scots pine, after an absence of centuries. "We have a broad range of trees from different countries and from different climactic zones at Birr, and I'm always looking for the introduction of new ones, to see which fit and which don't. I've just returned from four or five weeks in the Andes looking at another tree, a Polylepis australis, which grows at 4,000m up in the mountains and should certainly be hardy here. So that's going to be my next one, maybe for my next birthday."

Thanks to human interference with its natural habitat, P australis is in trouble in its native Argentina, as indeed are redwoods in California. According to Clara Clark of Crann, "fire and drought are taking their toll; all the redwoods are threatened".

It is, she says, entirely appropriate that a diaspora project should focus on the fact that – sometimes by choice, sometimes by necessity – trees and people have to move around the world. “We’re giving people the chance to put down roots in Ireland. Some families can’t afford to come home, but with these trees they are home,” she says. “I think that’s magical.”

Native species

Birr is, in any case, doing its bit for native species with a thriving grove of recently planted oaks and a tract along the river that is known to the family as the wilderness.

“No one is ever allowed to touch anything there, unless there’s something invasive, in which case it’s taken out,” says Parsons. “But otherwise everything grows to its full length. And when it falls it’s left for insects and everything else. That’s where we were lucky enough to attract the otters.”

By dint of many years of hard work, he adds, the estate also has red squirrels and their allies, pine martens. If you want native red squirrels you have to wage an unpalatable war on the invasive greys. And if you want to have the world’s tallest trees you can’t just bung them in the ground and leave them. They’ve got to be managed, not just as saplings but as they grow. Hence that €500 sponsorship figure, which will provide a trust fund for the ongoing management of the grove.

“We’re trying to make the planting as natural as possible,” says Parsons. “I don’t want the grove to look like a forestry block, or a circle, or an avenue – and what we will be interspersing between the trees will be entirely native. It’s an area that is very strong in holly, spindle and juniper.”

We’ve arrived at the stately sequoia that claims the title of the estate’s biggest redwood. As photographs are taken of Lord Rosse with two of the grove’s first saplings, which will go into the ground when planting gets under way in spring 2017, I wonder aloud about what, exactly, constitutes a grove. “I think 3,000 trees is a lot for a grove,” his daughter, Lady Alicia Clements, offers. On the other hand the Eden Project, in Cornwall, has been hugely criticised for calling the 40 coast redwoods it planted earlier this year a forest. “A grove is dozens,” she says. “A wood is hundreds. A forest is many thousands – well, the definition of a forest is that it supports its own ecosystem.” So technically it will be somewhere between the latter two, but, as Clara Clark points out, a “redwood wood” doesn’t have quite the right ring.

On the way back to the castle I ask Parsons whether he has a particular fondness for redwoods. "I have the greatest respect for the trees that make the tallest, finest trees of all," he says. "And I think there can be little finer than the Sequoiadendron giganteum. And also I have a fascination for what will grow longest. I just love the idea of trying to succeed with a grove here that will last for literally thousands of years."

What will Ireland be like when these trees are soaring into the Offaly skies in 2,000 years’ time? Will Ireland even exist? Will Offaly? The planet may be overrun with people. Or there may be no people left. Nobody knows. Meanwhile, Lord Rosse is busy with a more mundane calculation. “Five hundred euro over two millennia,” he says. “It’s really not very much when you work it out on a per-annum basis.”

It is, in fact, 25c a year. As to whether potential sponsors can be persuaded that they’re getting a botanical bargain at Birr, well, that remains to be seen.

DON’T TRY THIS AT HOME: HOW TO GROW A GIANT SEQUOIA

Although they share many characteristics, including that distinctive cinnamon-red bark, giant sequoias (Sequoiadendron giganteum) and coast redwoods (Sequoia sempervirens) are actually distinct species from different biological genera. Coast redwoods grow faster, so they protect the giant sequoias as they develop. But there’s something of a Jack and the Beanstalk feel about getting a 100m tree from a seed the size of a flake of oatmeal.

So how do you grow a giant redwood? Do they need special pampering? “Not really,” says Peadar Collins of the Irish Tree Centre in Cork and a director of Crann, who sourced the trees for Birr’s new grove two years ago and has been looking after them since. “They’re a fairly straightforward plant. We potted them up using slow-release fertiliser; then we potted them on a second time, to furnish good strong roots.” Daily watering and protection from marauding rabbits are about the height of it. “They grow very vigorously, and once they hit the soil in Birr they should take off.”

So the moral of the story is that you too could grow a giant redwood. But don’t. Or you’ll be fighting with your neighbours for the next 2,000 years.

See also "There is a tree for every kind of garden", at iti.ms/2ea8Siv, and "How many rooms are there in the castle? It depends on what you call a room", at iti.ms/2dHVnum